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91 Cards in this Set
- Front
- Back
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Differentiate between nonspecific and specific defenses.
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Nonspecific - innate, respond immediatly and in the same way to any/all foreign substances; give specific the time needed to activate
Specific - acquired immunity; develop after birth; against a specific invader; triggered by antigens that are recognized by T or B lymphocytes |
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Between nonspecific and specific defenses, which is innate? Which is acquired after birth?
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- Innate = non-specific
- Acquired = specific |
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What role do the skin and mucous membranes play in protecting the body?
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- non-specific defenses
- physical membranes prevent approach and deny access to pathogens - separate internal from external environment |
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Identify the accessory structures and secretions of the skin and mucous membranes which increase the effectiveness of the body's mechanical barriers.
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- hairs - cillia in resp. tract keep dust/germs out by beating
- sebum - contains antibacterials, acidic - lysosome - in many watery secretions (tears, saliva, sweat) - mucus - traps and gets rid of substances - gastric juice - kills/destroys some eaten substances |
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What are the two primary types of phagocytes in the body?
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- Granulocytes - brief life-span; eats about 25 bacteria b4 they die (about an hour) b/c oxidative bursts cause intracellular damage; neutrophils mosly and some eosinophils
- Macrophages - wandering and fixed |
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Name and describe the five general steps involved in phagocytosis.
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- Chemotaxis - move to area
- Adhesion - specialized receptors allow them to attatch to pathogens (although some escape) - Ingestion - pseudopods! - Digestion - fuse with phagolysosome inside - Killing - oxidative burst where all enzymes in phagolysosome are activated Note: non-digestible materials are held in residual bodies inside of cells |
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Compare and contrast wandering and fixed macrophages
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Wandering - go wherever the "call is"; usually die sooner b/c they are fighting so much
Fixed - found in one tissue only, and only go into action if that tissue is invaded |
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What cellular organelle contains the enzymes required for intracellular digestion of microbes and particular matter?
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Phagolysosomes
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What is a natural killer (NK) cell?
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- large granular lymphocyte
- attack their targets by releasing perforins to cause cytolysis of target cell - targets cells bearing abnormal/unusual surface markers (like precancerous cells and virally affected cells) |
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What role do NK cells play in defending the body?
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- Function of immunologic surveillance
- Adhere to cells with abnormal proteins, and cause cytolysis - Targets cells bearing abnormal/unusual surface markers (like precancerous cells and virally affected cells) |
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How do NK cells destroy their target cells?
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- adhere to abnormal proteins
- golgi apparatus moves towards the attatchment point, releases perforin - perforin makes holes in the membrane - loss of ions, plasma into ICF - cell ruptures and dies (cytolysis) |
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What are the four cardinal signs of inflammation?
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- Swelling
- Redness - Heat - Pain |
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What physiologic events underlie each of the cardinal signs of inflammation?
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- Swelling - Capillaries leak fluid b/c of excaped plasma proteins; inc. IFHP; edema
- Redness + Heat - caused by release of chem (histamines, prostaglandins, kinins, complement) from (phagocytes, lymphocytes, damaged cells, mast cells, blood); cause inc. in blood flow (hyperemia) which causes inc. metabolic rate of cells (heat) and lots of rbcs (redness/erythemia) - Pain - the edema from the leaking capillaries presses on the free dendritic endings that sense pain; also the chemicals that are released cause pain |
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Identify and describe the major events of the inflammation process.
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- Vasodilation and inc. vascular permeability - caused by release of chem (histamines, prostaglandins, kinins, complement) from (phagocytes, lymphocytes, damaged cells, mast cells, blood); cause inc. in blood flow (hyperemia) which causes inc. metabolic rate of cells (heat) and lots of rbcs (redness/erythemia)
- Phagocytic mobilization - they pour into the blood stream quickly - 4-5x more in 1 hr (esp. neutrophils) - Phagocytosis - for clean-up of area; takes longer, but they don't die off quickly like the neutrophils |
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Describe the process of a phagocytic mobilization.
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- Leukocytosis - inc. wbcs in bloodstream (esp. Neutrophils, and fewer monocytes)
- Margination/pavementing - cling to walls of blood vessels and slow down - Diapedesis/emigration - move out into interstitial space; made easier b/c cap. are now more permeable - Chemotaxis - to injury/damage site |
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What is a virus?
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ultramicroscopic infectious agent that replicates itself only within cells of living hosts; many are pathogenic; a piece of nucleic acid (DNA or RNA) wrapped in a thin coat of protein
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Why do viruses invade cells of the body?
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- they aren't live/can't replicate by themselves
- they want to take over the host cell's system in order to replicate themselves |
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What are interferons?
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- a family of small proteins that act as antiviral agents
- take over of a cell causes it to release interferons - bind to receptors in neighboring cells and blocks viral reproduction in that cell - slows the spread of the virus - not virus specific |
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What roles do interferons play in enhancing the body's resistance to infection and disease?
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- take over of a cell causes it to release interferons
- bind to receptors in neighboring cells and blocks viral reproduction in that cell 3 types: - Alpha-interferons: attract and stimulate NK cells - Beta-interferons: reduce local inflammation in a damaged tissue - Gamma-interferons: stimulate macrophage activity to clean up the cytolysis |
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What type of molecules make up the complement system?
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- a group of proteins that are present in the blood/membranes in the inactive state
- they enhance other parts of the non-specific defenses |
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Identify and briefly describe the two pathways of complement activation.
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- both pathways activate C3 by cleaving it
Classical Pathway - B-lymphocytes produce certain antigen-antibody complexes that activates C1 and then eventually C3; the faster pathway, so it's usually used Alternative Pathway - interaction b/w complement proteins and certain polysaccharides on invading pathogens makes a big complex that will cleave C3; slower |
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What are the effects of complement activation?
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- Cytolysis - via memtrane attach complex (MAC); pumches holes in membranes
- Enhances inflammation - causes release of histamine from mast cells; dilates arterial cells in area; initiates chemotaxis for phagocytes - Enhances phagocyte chemotaxix - moving closer to complement proteins; chemoattractants - Opsonization - enhances phagocytosis by adhering to the microbe surface so it's easier for the phagocyte to grab on and eat it (mac. has receptors for the complement protein) - Inflammation - Fever - systemic high temp. |
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Describe the physiology of fevers (i.e. why do fevers develop?).
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- thermoregulatory center in preoptic area of hypothalamus is reset higher
- toxins/antigen-antibody complexes/antigens act on macrophages or hypothalamus to secrete interleukin I - acts as a pyrogen (feber producing substance that circulates in blood) - Pyrogens - inc. cyclooxygenase pathway = inc. in prostaglandin production in preoptic center = thermostat reset - cutoff for fever: 37.2 C or 99 F |
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What are the two characteristics which distinguish immunity from the body's nonspecific defenses?
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- Specificity - directed against a specific antigen
- Memory - when immune system encounters antigen (primary immune response), it creates memory cells - Antigen comes again (secondary immune response... much faster) |
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What is an antigen?
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- any substance that can mobilize the immune system and provoke an immune response (complete or incomplete)
- not necessarily harmful - all proteins and some glycoproteins in plasma membranes are antigens (but they don't elicit that response in your own body) - proteins are the strongest Ag |
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What two properties characterize a complete antigen?
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- immunogenicity - the ability to trigger an immune response by triggering lymphocyte proliferation and antibody production
- reactivity - ability to react specifically with the cells (lymphocytes) or antibodies produced in the immune response |
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What is the difference between a complete and an incomplete antigen?
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- Complete - immunogenicity (can trigger immune response) and reactivity (can react specifically with cells or antibodies produced in immune response)
- Incomplete - reactive but not immunogenic |
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What is an antigenic determinant (i.e. epitope)?
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- the region of an Ag that is immunogenic
- the lymphocyte or antibody binding site - most Ag have a number of epitopes, so a single antigen could activate multiple populations of lymphocytes |
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What is the function of major histocompatibility complex (MHC) antigens?
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- self-recognition
- also called the "human leukocyte antigen" (HLA) - in plasma membranes of all cells - T cells recognize the MHC mollecule |
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What are the two classes of MHC proteins? Which cells of the body express each type?
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- Class I (MHC-1) - created in virtually all body cels
- Class II (MHC-II) - present on y in the membrane of antigen-presenting cells; cells in thymus, and some activated lymphocytes |
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Where do immature lymphcytes originate?
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- come to thymus as 4- and 8- from bone marrow
- begin to express 4,8, TCR (t-cell receptor) in thymus - then the negative and positive selection begins |
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From what undifferentiated cell do lymphocytes originate?
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- Originally, the first split is between myeloid stem cells and lymphoid stem cells
- myeloid stem cells - all other cells of blood etc - lymphoid stem cells - become lymphocytes |
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Where do T and B lymphocytes mature and become immunocompetant?
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- T cells - become immunocompetant in the thymus
- B cells - become immunocompetant and self-tolerant during maturation in the bone marrow |
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What lymphocyte type is associated with cell-mediated immunity? with humoral immunity?
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- Cell-mediated - T lymphocytes
- Humoral immunity (w/antibodies) - B lymphocytes; a little help from CD4 T cell |
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Which pre-T cells are eliminated during the first stage of T cell maturation? What is this stage called? Where (specifically) does this stage take place?
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- eliminates pre-T cells that cannot recognize self-MCH expressed by the epithelial cels
- The positive selection stage - Occurs in the cortex of the thymus (in the cortical epithelium) |
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Which pre-T cells are eliminated during the second stage of T cell maturation? What is this stage called? Where (specifically) does this stage take place?
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- Eliminates pre-T cells that recognize and respond to self-antigens (would start autoimmune responses)
- The negative selection stage - Occurs in the medulla of the thymus |
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Explain the difference between deletion (i.e. apoptosis) and anergy.
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- Apoptosis - cell perforates itself and dies
- Anergy - cell is inactivated; enters prolonged state of non-responsiveness |
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Where in humans do B cells develop immunocompetance and self-tolerance?
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- in the bone marrow
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Which subset of T cells expresses CD4 antigen? CD 8?
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CD4 - Helper T cells
CD8 - cytotoxic/killer T cells |
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What is the role of antigen-presenting cells (APCs) in an immune response?
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- role in activating lymphocytes
- send 2 signals @ once: antigen presentation and costimulation - APCs: dendritic cells, macrophages, activated B lymphocytes - insures that T cells don't get activated by your body's own cells |
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What three types of cells function as antigen-presenting cells?
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- dendritic cells (DCs)
- macrophages - activated B cells |
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Describe the difference between endogenous and exogenous antigens.
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Endogenous - foreign particles that are synthesized within a body cell; (viral antigens, cancerous body cells make proteins, cell itself makes toxic materialw when experiencing bacterial infection)
- Exogenous - foreign Ags that have been phagocytized from the ECF and degraced within a phagosome |
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Explain how endogenous and exogenous antigens are processed and complexed with MHC proteins
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- Endogenous - abnormal peptides in cell cytoplasm are transported to ER, loaded onto MHC-1 proteins; released from golgi apparatus; inserted in plasma membrane
- Exogenous - ingestion of Ag inside a phagosome, fuses with lysosome and digested into polypeptide fragments; fusion of a vesicle with MHC-II that has been produced inside of it; assembly of Ag-MHC-II complexes; inserted by exocytosis into plasma membrane |
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What class of MHC protein is complexed with endogenous antigens? with exogenous antigens?
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- Endogenous - MHC-I
- Exogenous - MHC-II |
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Identify and describe the three basic stages of the cell-mediated imune response.
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Antigen recognition - Inactive T cells have receptors that recognize Ag either with MHC-I (for CD8 cells) or MHC-II (for CD4 cells); need costimulation simultaneously
- Proliferation and differentiation - activated lymphocyte enlarges and proliferates into clones, then differentiates into: helper, cytotoxic, memory and supressor T cells - elimination of antigens |
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How do APCs interact with T lymphocytes to activate a cell-mediated immune response?
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- APCs present either MHC-1 or MCH-II antigen complex
- activates CD8 and CD4 respectively, if costimulation is simultaneous - costimulation: T-helper secretes interleukin II for the CD8 T cell; APCs produce cytokiner/interleukin 1 to stimulate T helper cells |
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What two signals are required to activate T cells?
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- antigen recognition
- costimulation signal - costimulation: T-helper secretes interleukin II for the CD8 T cell; APCs produce cytokiner/interleukin 1 to stimulate T helper cells |
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What are the two primary classes of T lymphocyte involved in an immune response?
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Helper T cells - CD4; regulatory cells
Cytotoxic T cells - CD8; directly attack and destroy their targets |
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Describe the role of the two primary classes of T lymphocytes involved in an immune response.
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Helper T cells - CD4; regulatory cells (coordinate specific and nonspecific responses via secretion of cytokines); interleukin II stimulated T cells/CD8 cells, costimulation signals for B cells; cytokines stimulate NK cells, attract macrophages, stimulate phagocytosis and antibody production by B cells
Cytotoxic T cells - CD8; directly attack and destroy their targets (invaded host cells, certain cancer cells, transplanted organs);Kill either through cytolysis of cells with perforin or secretion of lymphotoxin to break down DNA |
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What is the importance of memory cells?
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- reside in lymph tissue for a long time; carry out secondary immune response
- mount stronger, faster response - formed during primary immune response |
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Identify and describe the three basic stages of the antibody-mediated immune response.
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- B cell activation: B cell receptor (BCR) binds to antigen, phagocytizes it, loads it onto MHC II and presents it; now it's sensitized, but still not activated; T helper cell recognized Ag-MHC-II complex on B cell and secretes costimulatory cytokines = B cell activated!
- Proliferation - B cell clones itself; differentiation into plasma cells with lots of ER and memory B cells - Plasma cells secrete antibodies from ER into body fluids w/same receptor as their BCR |
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Name the specialized type of B lymphocyte which secretes antibodies.
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- plasma cells
- differentiated from basic B cells - other cells remain as memory B cells |
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Describe the general structure of an antibody.
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- protein molecule composed of four polypeptide chains linked together with disulfide bonds (2 heavy chains, 2 light chains; looks like a Y)
- Each chain: variable region at one end and constant region at another - Each immunoglobulin/antibody/Ag has 2 Ag binding sites |
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What is the function of the constant region of an antibody molecule? of the variable region?
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constant - determines antibody function - the effect after it binds to antigen (ability to bind to macrophages etc)
Variable - determines which antigen it will bind to; this part out at the end of the arm; each antibody has a difft. variable region |
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Identify and describe the mechanisms of antibody action.
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- Neutralization - neutralizes effectiveness of dangerous antigen (ex. keeps bacteria from adhering by covering adhesion proteins)
- Immobilization of bacteria - binds to flagellum or cillia - Agglutination - antibodies cross-linking membrane bound antigens into clot/clump which can't move, so macrophages can catch up - Precipitation- antibodies cross-linking soluble antigens into clot/clump which precipitates out of solution, so macrophages can catch up - Complement activation (classical pathway) - antibodies bind and activate complement proteins - Enhancecd phagocytosis - macrophage binding sites on antibodies help adhesion |
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How are antibodies grouped into classes?
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- Igs grouped according to C (constant) region of the H (heavy) chains
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Identify the five classes of antibodies and describe the general role of each.
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IgD - membrane bound on mature B cells, where serves as Ag-receptor; exact role unknown; <1%
IgM - monomer attatehce to B cell mem.; first Ab to be expressed; 1st class of soluble Ab to be secreted during primary immune reponse; large/confined to blood vessels; numerous Ag binding sites, so clumps quickly and activates compliment IgG - 80%; main one (both primary and secondary response); only one which crosses placenta for passive neonate protection; activates complement; involved in neutralization, agglutination, opsonization IgA - predominant class of secretory Ig (in tears, saliva, nasal secretions, bronchial/digestive tract mucus, mammary gland secretions); protects mucosal surfaces by coating bacteria and viruses IgE - <.05%; secreted by plasma cells + taken up by specific receptros on mast cells and basophils in CT surrounding microvasculature; allergic response in immediate hypersensitivity reactions; evolved as immune response to intestinal parisites |
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Describe the differences between a primary and secondary immune response.
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Primary - 1st time immune system encounters a specific antigen
Secondary - less lag time, antibody titers peak at a much higher level |
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Distinguish between active and passive immunity.
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- Active - develops through Ag encounter and subsequent immune response (can be naturally or induced w/vaccine)
- Passive - body's own immune system isn't challenged, so no antibodies or memory cells are produced (can be natural or artificial) |
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Which type of immunity, active or passive, results in the formation of antibodies and memory cells?
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- Active immunity - where immunity develops through an Ag encounter
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Do vaccines promote active or passive immunity (or both)?
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- Both
- Active if you inject a weakened form of the disease - Passive if you're injecting immune serum (gamma globulin) |
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Describe an example of naturally acquired passive immunity and an example of artificially acquired passive immunity.
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Naturally - antibodies move across placenta from mom to fetus
Artificially - injection of imune serum (gamma globulin) |
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vaccine
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artificially inducing active immunity by injecting antigens into the body (usually weakened ones)
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Cytolysis
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the bursing or lysis of a cell
- caused by perforins released from NK cells or by Membrane attack complex (MAC) as part of the complement system |
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perforins
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released from NK cells golgi apparatus
makes holes in membrane of target cell; causes loww of ions into ECF eventually cell ruptures and dies |
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opsonization
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- done by antibodies and complement
- enhances phagocytosis by adhering to the microbe surface, making it easier for the macrophage to grab on |
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pus
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the dead or dying stuff in a wound
- accumulation of material (w/phospholipids etc) - frequently there, but we only see it when it's at the surface |
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abcess
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pus accumulated in an enclosed space where its hard to remove it (teeth, jaw...)
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membrane attack complex
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- MAC
- one of the ways that the complement (C3) can enhance the body's defenses - works like perforin - a circle of complement proteins that punches holes in microbial walls |
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immunogenicity
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the ability to trigger an immune response by triggering lymphocyte proliferation (and thus antibody production)
- one of the two functional characteristics of antigens (other one is reactivity) |
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reactivity
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the ability to react specifically with the cells or antibodies procuded in the immune reponse
- one of the two functional characteristics of antigens (other one is immunogenicity) - if an antigen only has reactivity it is an incomplete antigen |
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Human leukocyte antigen (HLA)
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- MHC - the major histocompatibility complex
- found in plasma membrane of all cells - the way that we recognize our own cells |
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hapten
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- an incomplete antigen
- reactive but not immunogenic - antibodies react with the hapten alone, but the hapten forms a complex with an intrinsic protein and THEN it triggers antibody production - so by itself it can't trigger an immune response, but it can react with an immune response that is already there |
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immunocompetant
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B or T lymphocyte displays one unique type of Ag receptor on it's surface
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phagosome
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- inside a phagocyte
- a vesicle of material that has been ingested |
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phagolysosome
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- inside a phagocyte
- a vesicle of material that has been ingested that has fused with a lysosome full of lysosyme |
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lysozyme
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an enzyme found inside lysosomes in phagocytes
- inside a phagolysosome it breaks down whatever the phagocyte ingested |
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lymphotoxin
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- secreted by cytotoxic T cells as one of their two kiling mechanisms (other one is secretion of perforin)
- moves into target cell through pores - breaks down targe cell DNA |
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clone
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- an activated lymphocyte enlarges and then proliferates, forming clones
- identical to the original cell - differentiates into: helper T cells, cytotoxic T cells, memory T cells |
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interferons (IFNs)
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- small proteins that acta as antiviral agents
- the take-over of a cell causes it to release INFs - INFs bind to receptors in neighboring cells; block viral reproduction in neighboring cell - slows spread of virus - not virus specific |
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opsonin
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An antibody or product of complement activation in blood serum that causes bacteria or other foreign cells to become more susceptible to the action of phagocytes
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oxidative bursts
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- occur in granulocytes (neutrophils, eosinophils etc)
- they eat bacteria and then oxidative bursts (where all enzymes in them are activated) occur and kill the bacteria - kills the wbc itself after eating about 25 bacteria |
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residual body
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when a macrophage eats something non-digestable, it will keep it inside rather than ejecting it
keeps it in a residual body |
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self-recognition
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the ability of the body's immune system to recognize self-identifying antigens on the body's own cells
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self-tolerance
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the absence of an immune response directed against a person's own tissue antigens
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histocompatibility
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the degree of similarity between the histocompatibility antigens of two individuals. Histocompatibility determines whether an organ transplant will be tolerated
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leukocytosis
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marked increase in white blood cells: a marked increase in the number of white blood cells leukocytes, usually because of infection or disease
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Interleukin-2 (IL-2)
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- secreted by helper T cells; stimulates killer T cells (CD8)
- the costimulation signal required at the same time as Ag recognition occurs |
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Interleukin-1 (IL-1)
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- the costimulation signal required at the same time as Ag recognition occurs
- produced by APCs (macrophages and Dendritic cells) - Stimulates helper T cells (CD4) |
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cytokine
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protein produced by cells: any protein secreted by lymph cells that affects cellular activity and controls inflammation
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immunologic surveillance
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the constant monitoring by the immune system of microorganisms, foreign tissue, and diseases caused by altered cells, especially cancer cells
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